This invention relates to an offroad running motorcycle and more particularly to an improved drive and suspension arrangement for such a vehicle.
Recently, it has been proposed to employ large low pressure balloon type tires on at least the driving wheel of motorcycles intended for off the road application. Although the low pressure balloon tire provides some suspension in and of itself, for improved ride and handling, it is desirable to incorporate an additional suspension system for the rear wheel. Such vehicles normally employ chain drives for driving the rear wheel and the use of balloon tires gives rise to certain problems in connection with the chain drive. That is, because the tire is as wide or wider than the frame of the motorcycle, the driving sprocket for it must be positioned at the side of the tire as must the driving chain. If a single chain is used from the engine to the rear wheel, this means that the driving sprocket from the transmission or engine must be placed laterally outwardly of the frame. This encroaches in the area where the rider's feet normally are and can give rise to an uncomfortable riding position.
In order to avoid the use of such laterally displaced driving chains in the area of the engine, it has been proposed to use a two chain drive wherein the engine drives a first chain which drives an idler shaft, which idler shaft in turn drives the rear wheel. In this way, the first chain may be placed narrowly within the confines of the motorcycle frame and the rider's seating and foot position will not be adversely affected. An example of such an arrangement is shown in Japanese Published Application No. 49-27375, published July 25, 1974.
However, the disadvantages of the construction shown in that patent is that the intermediate driving chain from the engine to the intermediate shaft is placed directly behind the final driving chain which makes servicing of the intermediate chain difficult, if not impossible, without removal of the final driving chain.
It is, therefore, a principal object of this invention to provide an improved driving chain arrangement for a motorcycle of the type embodying a balloon tire.
It is another object of the invention to provide an improved multiple driving chain arrangement for a motorcycle or the like wherein the individual chains may be conveniently serviced without removing other chains.
In connection with motorcycles having suspended rear wheels, including those of the balloon tire type, it is the normal practice to use a trailing arm suspension for the rear wheel. With off the road vehicles, it is particularly important to use a relatively long trailing arm construction so as to employ large suspension movements due to the wide variety of terrains over which the vehicle is operated. Where a dual chain drive is employed, however, it has been difficult to employ such long trailing arms due to the difficulty in mounting the chains in such a way that their tension will not change during suspension movement and in order to avoid wear of the chains. One way this can be done is by placing the intermediate shaft in line with the pivot shaft of the trailing arm as shown in the noted Japanese published application. One disadvantage of such an arrangement is that the intermediate driving chain is quite short in length and it is difficult to have its tension adjusted. Also, this arrangement tends to reduce the permissible length of the trailing arm suspension.
It is, therefore, a further object of this invention to provide an improved driving arrangement for a motorcycle or the like having a trailing arm suspension.
It is another object of this invention to provide a chain driving arrangement for the wheel of a vehicle supported by a trailing arm in which multiple chains are employed and the configuration is such that the tensioning of the chains does not vary during suspension movement.
As has been noted, the combination of a balloon tire and a suspension system has particularly utility in improving the handling of off the road motorcycles. However, due to the use of the extremely wide rear tires, it has been difficult with prior art constructions to locate the suspension elements in such a manner that they do not encroach upon and adversely affect the seating position.
It is, therefore, a still further object of this invention to provide an improved suspension arrangement for a motorcycle or the like.
It is a further object of this invention to provide an improved motorcycle suspension wherein a single centrally positioned suspension unit can be utilized with a wide balloon tire.